The Basic Parts of Generators
When an emergency or natural disaster knocks out your power supply, generators provide the electrical energy you need to keep running. They come in a variety of sizes and types, with applications from standby power for homes to large industrial and commercial power plants. These machines work in tandem with engine units to turn gasoline, solar or diesel fuel into usable electricity. While some generators are designed for portable use, others are built to be housed in a permanent installation. Understanding the parts of a generator is key to properly maintaining it and keeping it in good working condition.
The basic principles of generators are based on electromagnetic induction. In order to produce electricity, a generator must first generate magnetic flux in the rotor and create a current in the armature. A small amount of remanent magnetism in the iron core is enough to get things started, but to increase the current in the armature the generator must spin faster and generate more magnetic flux in the rotor. This process is known as the bootstrap and continues until the armature current reaches a steady state.
To generate more current, the generator uses a set of secondary windings on its iron core known as exciter windings. These are connected to a set of rotary rectifiers that convert the AC voltage into DC current. The DC current is then fed to the rotor / armature where it induces a larger magnetic field. The generator now produces a higher output AC current.
Many generators also have an alternator which works to produce AC and DC current in a similar fashion to a car's alternator. However, unlike the alternator in a vehicle, which is powered by the car's engine, generators are powered by a separate internal engine unit. Depending on the size of the generator, this engine may be gas, diesel or even natural gas.
Like your automobile, a generator requires a heavy-duty battery and fuel tank to maintain its basic functions. Smaller household generators typically use gasoline, while larger commercial varieties feature diesel engines.
Some larger generators, such as those used at electric power stations, require a special procedure known as black starting to excite the fields of the generator before they can start producing power again. This is often necessary when large areas of the power grid have been shut off due to islanding or other causes. Black starting is also common when a large generator needs to be restarted after a long period of time has passed since its last shutdown. As you can imagine, this can be a very time-consuming and labor-intensive process.